# std::conj(std::complex)

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< cpp‎ | numeric‎ | complex

Defined in header `<complex>` |  |
| (1) |
template< class T > std::complex<T> conj( const std::complex<T>& z ); |  | (until C++20)
template< class T > constexpr std::complex<T> conj( const std::complex<T>& z ); |  | (since C++20)
Additional overloads (since C++11) |  |
Defined in header `<complex>` |  |
| (A) |
std::complex<float> conj( float f ); std::complex<double> conj( double f ); std::complex<long double> conj( long double f ); |  | (until C++20)
constexpr std::complex<float> conj( float f ); constexpr std::complex<double> conj( double f ); constexpr std::complex<long double> conj( long double f ); |  | (since C++20) (until C++23)
template< class FloatingPoint > constexpr std::complex<FloatingPoint> conj( FloatingPoint f ); |  | (since C++23)
| (B) |
template< class Integer > constexpr std::complex<double> conj( Integer i ); |  | (until C++20)
template< class Integer > constexpr std::complex<double> conj( Integer i ); |  | (since C++20)

1) Computes the complex conjugate of z by reversing the sign of the imaginary part.

A,B) Additional overloads are provided for all integer and floating-point types, which are treated as complex numbers with zero imaginary component. | (since C++11)

### Parameters

z | - | complex value
f | - | floating-point value
i | - | integer value

### Return value

1) The complex conjugate of z.
A) std::complex(f).
B) std::complex<double>(i).

### Notes

The additional overloads are not required to be provided exactly as (A,B). They only need to be sufficient to ensure that for their argument num:

- If num has a standard(until C++23) floating-point type `T`, then std::conj(num) has the same effect as std::conj(std::complex<T>(num)).
- Otherwise, if num has an integer type, then std::conj(num) has the same effect as std::conj(std::complex<double>(num)).

### Example

Run this code

    #include <complex>
    #include <iostream>

    int main()
    {
        std::complex<double> z(1.0, 2.0);
        std::cout << "The conjugate of " << z << " is " << std::conj(z) << '\n'
                  << "Their product is " << z * std::conj(z) << '\n';
    }

Output:

    The conjugate of (1,2) is (1,-2)
    Their product is (5,0)

### See also

abs(std::complex) | returns the magnitude of a complex number (function template)
norm | returns the squared magnitude (function template)
polar | constructs a complex number from magnitude and phase angle (function template)
C documentation for conj

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